(1) Field of the Invention
This invention relates to a process for using chemicals to stimulate oviposition in insects.
(2) Description of the Prior Art
Insecticides are not always effective or desirable for the control of many species of insects which cause enormous losses of food and fiber. Egg parasitoids of the genus Trichogramma are especially promising biocontrol agents because: (1) they parasitize a wide range of host insects, (2) they destroy the host in the egg so that no larval feeding damage occurs, (3) they are readily manipulated and mass-reared in the laboratory, and (4) host-seeking chemicals are available to enhance the effectiveness of released and indigenous parasitoids in the field. Trichogramma spp. are the most widely studied entomophagous insects and are used for biocontrol on global basis both in developed and developing countries. Augmentative releases of these parasitoids are restricted by the expense associated with the production of host eggs. Economical mass production of parasitoids on artificial diets in quantities suitable for augmentative releases requires techniques for the collection of large numbers of Trichogramma spp. eggs.
Eggs were first collected by dissecting them from parasitized host eggs. Next (Rajendram and Hagen, "Trichogramma Oviposition into Artificial Substrates" Environ. Entomol. 3:399-401 (1974)) reported that Neisenheimer's solution (a mixture composed mostly of NaCl and with much smaller amounts of NaHCO.sub.3, CaCl.sub.2, and KCl) stimulated oviposition by Trichogramma californicum. Results were poor and erratic. It is significant that Rajendram "Some Factors Affecting Oviposition of Trichogramma californicum (Hymenoptera:Trichogrammatidae) in Artificial Media" Can. Entomol. 110:345-352 (1978) concluded that "no particular salt, amino acid, or vitamin tested was seen to be essential for eliciting oviposition". Hoffman et al, Annals Entomological Society America, 68:335-6 (1975) used insect hemolymph to elicit oviposition and this also has been used by several Chinese workers. The Chinese also have used solutions of salts, amino acids, proteins, protein hydrolyzates, and artificial diets containing amino acids, salts, etc., but all appear to be weak ovipositional stimulants for Trichogramma. A mixture of either magnesium salts or trehalose and several amino acids stimulated oviposition by the parasite Itoplectis conquisitor.